I...almost wonder if Tax brings out one's hidden natures?
Well, The problem is this seems like it could be as much of a red flag as an actual thing, given Ichabod REALLY oughta be able to make his case well enough that he's not dismissed as being a conspiracy theorist for that Tax is making Stilez smart theory.

Actually, if you want an ABSOLULTELY IMPOSSIBLE, BUT TOO COOL NOT TO BE TRUE, explanation on who Tax is, there is a good one. She's Princess Rheiko. Okay, sure, Tax looks about the same age that Avatar looks (if not a bit younger), and that's younger than Princess Rheiko was when she disappeared, but she could have undergone massive, possibly Mad Science related, surgery to stick her into her current dog-like body.

OF COURSE!
It is so obvious now! There had to be a quantum deagification component or she would have normal dog traits instead of puppy traits! It is becoming so clear! (For those wondering deagification is pronounced de-age-ification. Spelling it like that looked weird and maybe made grammar cry.)

Don't know who that guy was. What? He was me? You say I'm just pretending I didn't say that? That is preposterous!

Clearly Tax has some sort of suspicious effect, and not just on Stilez! I suspect that a cadre of Mad Scientists and Military Brass decided they needed a way to neutralize or preferably control Stilez, but had no idea how to manage that. Therefore the Mad Scientists, using Mundorem Shapeshifting tech combined with Trandozian Bioengineering (callbacks!) devised an amorphous creature designed to seek out the most powerful enemy it could find and analyze its weakness and transform to exploit that weakness: the Transforming Adaptive Xenomorph!! Once the T.A.X. located Stilez, it determined after observation that her weakness was adorable puppy-girls and transformed accordingly. Since evil-war-machine and adorable-puppy-girl are incompatible, it lost most of its prior programming in the transformation process, but it still retains its mission to make Stilez more controllable and less dangerous.

@Eikkert - That's exactly why that can't possibly be it. The most likely explanation is NEVER what it actually turns out to be in the Far Out There universe. In fact, the least likely most convoluted improbable explanation is usually your best bet, right up to the sudden surprise twist that makes even that option more complex and unlikely!